The present invention relates to an ink jet recording apparatus and, more particularly, to an ink jet recording apparatus equipped with a head washing device and suitable for use in, for example, a peripheral equipment of a computer or a color printer.
An ink jet printing in which air flow joins ink droplets has been known in the art as exemplified by the system shown and described in U.S. Pat. No. 4,106,032. In the system described in this patent, a jet of ink is caused to issue from an ink nozzle of an ink jet head in the form of a succession of tiny individual ink droplets of a varying size depending on the instantaneous value of an input signal which is to be recorded, and carried to a recording medium with air flow from an air nozzle of the ink jet head. The ink nozzle is moved across the surface of the recording medium so that the ink droplets are ejected to desired print positions.
In this system, when the ink jet head upon completion of the printing has reached the final recording point, the nozzle surface of the ink jet head has been contaminated by contaminants such as ink splashed back from the surface of the recording paper and paper dusts.
A cleaning device has been known which is designed to remove these contaminants from the nozzle surface thereby cleaning the nozzle surface, as shown in FIG. 5 attached to the specification of U.S. Pat. No. 4,364,065. This cleaning device has a head cleaner which is adapted to wipe the nozzle surface of the ink jet head when the head is moved to a position beyond one end of the recording drum by the feeding mechanism, thereby scraping off the contaminants from the nozzle surface. The contaminant scraped off from the nozzle surface moves downward by its weight along a gutter formed in the cleaner and is collected in a receptacle.
In this system, the contaminant is heavily accumulated in the cleaner as the recording is conducted frequently, so that the cleaning effect is gradually impaired, although deposition of the contaminant on the nozzle surface is avoided. In fact, it is very difficult to keep clean the nozzle surface with the head cleaner which has been stuffed with the contaminants scraped off from the nozzle surface. In addition, since the nozzle surface is scraped by the head cleaner, there is a risk that the air nozzle is clogged with the contaminant which has been scraped off from the nozzle surface, causing various detrimental effects or troubles.
On the other hand, the specification of U.S. Pat. No. 4,106,032 discloses an ink jet head in which the air pressure applied to the air chamber of the head and the air pressure applied to the ink tank are adjusted so as to maintain a good balance of pressure in the region around the ink nozzle, thereby improving the discharge characteristics of the head. In this type of ink jet head, the desired balance of pressure is maintained on condition that the air is jetted from the air nozzle. Therefore, any blockage of the air nozzle, even when it is a temporary one, impairs the balance of the pressure resulting in various troubles such as introduction of air into the ink chamber of the ink head. For this reason, it has been prohibited to apply the head cleaner to the ink jet head of the kind described. The air nozzle tends to be clogged also with ink adhered to and dried on the head nozzle surface, so as to impair the balance of the pressure resulting in the troubles mentioned above.